Study On The Enrichment Regularity Of Indium In Dachang Ore-field, Guangxi

With the guideline of the geochemical theory of rare earth element (REE), starting from analyses of regional metallogenic background of Dachang mine fields in Guangxi province, geological characteristics, geochemical characteristics and metallogenic genesis are studied systematically and deeply by using the knowledge of petrology, structural geology, REE geochemistry, geochemistry of trace element, stable isotope geochemistry and inclusions geochemistry. On the basis of summarizing of metallogenic regularities roundly, researches on the enrichment regularity of indium have been done.Proceeding with analyses of regional metallogenic background of Dachang mine fields by using Diwa metallogenic theory, the author has explained that Dachang mine fields has undergone three big developing evolution stages, i.e. Pregeosyncline, platform and Diwa stage. The pregeosyncline period in which the protolith stratum of pre-Triassic was formed; during Indo-Chinese epoch, the region was arised and platform formed; When Yanshanian period, the platform was moved into Diwa stage by activating, large-scale tectonic and magmatic activities happed in that region, which was considered as significant forming stage of Dachang mine fields.The author, for the first time, have studied on the geochemical feature of the trace element and the REE of the country rock near orebody, magmatite and ore; pointed out the geochemical action feature of the trace element and REE in the ore-forming process and diagenetic stage, The physical chemical features suggest indium emplaced in relative oxidized and weakly alkaline ore-forming environment.The author, for the first time, has studied on the relationship between indium and other metallogenic element, and then discovers that there is positive relation between Sn and In. The similarity of geochemical behaviors of Sn and In made them migrate and deposit together. Sn play a very important role during the process of activating, migrating and entering sphalerite lattice. Negative relation between Sn and In show that In have entered the sphalerite lattice before the crystallization of sphalerite, in addition, it also proved that In tend to enter the sphalerite lattice under higher temperature.The author, for the first time, have studied on the relationship between indium and magmatite, the result shows that magmatite play a very important role during the diagenetic stage.The more near to the rock mass, the more high the content of indium.The research on the regional stratum and trace elemental feature of magmatite show that mineralizing materials are of multi-sources and are not derived from special stratum and magmatite. The geochemical feature of trace element Tongchejian group, Wuzhishan group, Liujian group and Nabiao group have in common with the feature of trace element of ore. It display generally that Light rare earth element enriched, weight rare earth element is flat, and Eu and Ce is loss. It also reflected ore inherited the rare earth element of host-rock.The research on the variety of indium in the different mean gradation illustrate that the content of indium kept positive relation to depth and proved that the content of indium has positive relation with metallogenic temperature in one orebody.Studied on the enrichment regularity of indium of Dachang mine field, based on the metallogenic genesis, rule and the variety of enrichment regularity in spatial, the author proposed some favorable place as follows:The first favorable place is around the Longxianggai granite rock mass. The formerly work focus on the granite rock mass which is liable with tin and antimony and neglect the study on marmatite, pyrite, and pyrrhotite. According the new exploration material and the rising of value of indium, plenty of pyrite, marmatite and pyrrhotite around the Longxianggai granite rock mass have very tremendous value.105 orebody, lied in the bottom of 100#orebody, is another large-scale enriched indium orebody. According the present exploration material,100 orebody is the known maximal indium reserves in the world, its metallgenic temperature is lower than the temperature of 105#, which is a tin spar-sulfide orebody with higher comprehensive grades. So, 105#orebody is the next key object. Tongkeng-Changpo mineral deposit is also another large-scale enriched indium orebody.